Morata has struggled on and off the pitch since arriving at Stamford Bridge for a then-club record fee of £58 million from Real Madrid in the summer of 2017, and had fallen behind Eden Hazard and Olivier Giroud in Sarri's striker pecking order in recent weeks.

"I think that Morata is a very good player," Sarri said. "I think that Morata has the characteristics for playing in my team. But Morata, one month ago, said he wanted to play in another team, so it was really very difficult for him to give us the 100 percent for his mental situation, I think.

"I think that Morata is potentially a very important player. From the physical and technical point of view, he is a very good player and suitable for my football. But the situation changed in the last month, so we needed to change."

As well as clearing the way for Morata to return to the Spanish capital, the acquisition of Higuain also represents a significant departure for Chelsea, who have been reluctant to sign players over the age of 30 in recent years.

Sarri personally recommended Higuain as Morata's replacement, and has a different view of when a footballer's best years end.

Alvaro Morata is expected to move back to La Liga.

"I think 31 and 32 is not really very old," he added. "I think that, for a striker, it's very difficult to score with continuity when they are 22, 23. So the best is from 27 to 32, 33. So I think [Higuain is] the right age."

Chelsea have an option to sign Higuain permanently next summer, but Sarri admitted that the 31-year-old needs to produce on the pitch for the rest of the season in order to convince the club to make a long-term investment in him.

"I don't know exactly the details of the contract, so it's very difficult for me to answer," Sarri said. "It's up to him, I think. He has to score, first of all. I think that, for a long-term contract, he has to do very well. He has to play. He has to score. He has to be useful for the team."

Chelsea could not register Higuain in time to feature in Thursday's second leg of the Carabao Cup semi-final against Tottenham at Stamford Bridge, when all eyes will be on the response of Sarri's players to his scathing public criticism of them following Saturday's limp 2-0 defeat against Arsenal.

"I didn't attack my players," he explained. "I told only my opinion about our problems. But I wanted that they realise the problem. I think it's my job.

"Of course, I have the responsibility also of the mental point of view, so the performance was my fault, of course. I said I am in trouble because it's very difficult to motivate them, but I didn't want to attack them.

"I don't know why [it's difficult to motivate them] otherwise it would have been easy for me. I don't know exactly the reason, or maybe there are 100 reasons. It's difficult, but we have to try something to improve in this.

"We are changing something in training, something in pre-match. We are trying to do our best, of course. But, for us, it's a problem -- not always, but even in some very important matches. So it's really very strange.

"When you play against Arsenal or Tottenham, you usually arrive at the match with a very high level of motivation and determination, but we made mistakes also in this kind of match. So it's very strange and we need to improve.

"But they agree with me. I discussed with the players after the match, and I said to them the same things as in the press conference. It's not a big problem. I want to be direct with them in private and in public."